Development of mechanical equivalent porous structures for 3D-printed artificial femoral heads

Abstract

The current artificial bone is unable to accurately replicate the inhomogeneity and anisotropy of human cancellous bone. To address this issue, we proposed a personalized approach based on clinical CT images to design mechanical equivalent porous structures for artificial femoral heads. Firstly, supported by Micro and clinical CT scans of 21 bone specimens, the anisotropic mechanical parameters of human cancellous bone in the femoral head were characterized using clinical CT values (Hounsfield unit). After that, the equivalent porous structure of cancellous bone was designed based on the gyroid surface, the influence of its degree of anisotropy and volume fraction on the macroscopic mechanical parameters was investigated by finite element analysis. Furthermore, a mapping relationship between CT values and the porous structure was established by jointly solving the mechanical parameters of the porous structure and human cancellous bone, allowing the design of personalized gradient porous structures based on clinical CT images. Finally, to verify the mechanical equivalence, implant press-in tests were conducted on 3D-printed artificial femoral heads and human femoral heads, the influence of the porous structure’s cell size in bone-implant interaction problems was also explored. Results showed that the minimum deviations of press-in stiffness (<15%) and peak load (<5%) both occurred when the cell size was 20% to 30% of the implant diameter. In conclusion, the designed porous structure can replicate the human cancellous bone-implant interaction at a high level, indicating its effectiveness in optimizing the mechanical performance of 3D-printed artificial femoral head.